controlling two different sound sources at same time

Using Win 10 pro on HP ENVY desktop.

Problem is that I have 2 different sound feeds that I am trying to hear at the same time, one as a background music, the other a fire department feed. When the fire department feed activates, I want to be able to quickly lower (or even turn off) just the music background. It appears that the volume control icon on the task bar (and also the on-screen slider button) controls the volume on the speakers themselves, not necessarily really controlling the incoming feeds.

The “open volume mixer” button has just two columns, left one is titled ‘Device,’ right one is ‘applications.’ So, I am looking for a way to separate these two feeds, hopefully – in the end - having a separate volume control button for each one.
The computer does not have a sound card, apparently everything in on the m-board. Would buying a sound card be the direction to go? Better still, I would like a software solution.
Is anyone aware if a way to have two different /system /sound applications on the VOLUME Mixer (right clicked on vol icon on task bar.

Need to mention that both feeds are apps, Accu-Radio and Broadcastify

thank-you